Reading and Writing Files in Python Explained Simply

Working with files lets your programs store and retrieve data. Python makes basic file operations easy with the open() function.

Opening a file

Use open() with the file name and mode.

Common modes:

• "r": read (default)
• "w": write (overwrites if file exists)
• "a": append (adds to end)
• "r+": read and write

file = open("example.txt", "r")

Always close the file when done:

file.close()

Better: use with (automatically closes):

with open("example.txt", "r") as file:
    # work with file
# file is closed here automatically

Reading from a file

Read entire content:

with open("example.txt", "r") as file:
    content = file.read()
    print(content)

Read line by line:

with open("example.txt", "r") as file:
    for line in file:
        print(line.strip())  # strip removes newline

Read all lines into a list:

with open("example.txt", "r") as file:
    lines = file.readlines()
    print(lines)

Writing to a file

Write (overwrites):

with open("output.txt", "w") as file:
    file.write("Hello, file!\n")
    file.write("Second line.")

Append:

with open("output.txt", "a") as file:
    file.write("\nNew appended line.")

Write multiple lines:

lines = ["First line\n", "Second line\n", "Third line\n"]

with open("list.txt", "w") as file:
    file.writelines(lines)

Simple examples

Save user input to a file:

name = input("Enter your name: ")

with open("names.txt", "a") as file:
    file.write(name + "\n")

Read and display a file:

try:
    with open("data.txt", "r") as file:
        print(file.read())
except FileNotFoundError:
    print("File not found.")

Important notes

• Use with to avoid forgetting to close files.
• Specify encoding if needed: open("file.txt", "r", encoding="utf-8")
• Handle FileNotFoundError when reading non-existent files.
• Writing in "w" mode deletes existing content.

Quick summary

• Open files with open() and use with for safety.
• Read with .read(), .readlines(), or loop.
• Write with .write() or .writelines().
• Use "r" for reading, "w" for writing, "a" for appending.
• Always handle possible errors.

Practice reading from and writing to simple text files. File operations are essential for persistent data in Python programs.